The present invention relates to a method of producing molten glass, to batch components for use in glass manufacture, and to a method of producing such batch components.
In the manufacture of glass, it is known to introduce a cold powdered mixture of raw materials, these being referred to in the art as cold batch, into a tank of molten glass and to react and melt the batch. This method is employed in the production of flat glass by the float process. A large tank is used for that process. It has been realised for some time that the present methods of melting glass are not particularly thermally efficient.
It is known to pre-heat the batch, for example by the use of exhaust gas from the burners which are used to heat the main melting tank. This gives some improvement in thermal efficiency, but it has been found that there are limitations to the degree to which the batch can be preheated. One such limitation is that some of the components form liquids at comparatively low temperatures and this causes the batch to become sticky and to block up the heat exchanger. It is well known that the first glassy phase to be formed in float glass batches is the product of a reaction of soda ash and some of the sand. It has been found that such batches become sticky at about 600.degree. C.
Proposals have been made to pre-react selected batch components. Russian Patent No. 716986 in the name of Kalinin Polytechnical Institute describes complex reaction schemes involving several reaction vessels and careful control of temperature and pressure.
These reaction schemes take no account of the materials handling problems that are associated with the use of naturally occurring raw materials: e.g. sticking, due to low melting point substances being formed on heating.